MMM wrote:Imagine every possible key chain and cell-phone strap in the universe.

Indeed! Last time I went to Tokyo I got a cell-phone strap of Hello Kitty dressed as an Akihabara Maid.

One of my favorite things to get a souvenirs are playing cards with photos of various famous places on them. That way you have something you can use (if like me you enjoy playing cards, that is) and you can enjoy all the sights, and they rarely set you back more than ¥700 or ¥800.